The present invention relates to a cryogen delivery apparatus for delivering a cryogen in a saturated state. More particularly, the present invention relates to such an apparatus in which a vessel serves as a phase separator in case the cryogen to be delivered is supplied as a two phase flow. The vessel contains a heat exchanger to convert subcooled liquid into a saturated liquid in case the cryogen is supplied as a subcooled liquid.
Cryogenic fluids such as liquid air or liquefied components of air are utilized in many cryogenic cooling and refrigeration applications. A common problem with supplying a cryogenic fluid is that the degree of cooling potential of the cryogenic fluid can vary with the condition of the fluid being supplied. For instance, subcooled liquid nitrogen has a different cooling potential than nitrogen supplied as a two phase flow. This problem is exacerbated in cooling applications that do not employ a feedback control system, but rather, rely on timers and the like to open and close cryogenic supply valves. An example of such a problematic application is where a cryogen is used in cooling blow molded plastic articles after having been formed. In many systems designed for such an application, the flow of the cryogen for each cooling cycle is controlled by a control valve which is opened for a pre-determined time period. The two phase flow form of the cryogen will have less cooling potential than the cryogen as a subcooled liquid. Moreover, the amount of subcooled liquid .that is supplied for a given valve opening will be greater than that of the cryogen supplied as a two phase flow due to the increased density of the subcooled liquid. Since the cooling potential of the cryogen will vary with its physical state, either plastic parts will not be cooled sufficiently or the cryogen will be wasted.
As will be discussed the present invention provides a practical solution to alleviate the problem set forth above by providing a cryogen delivery apparatus that serves as an interface between the liquid cryogen being supplied and the particular application for which the cryogen is being used. The interface provided by the present invention is one that insures that the cryogen will be consistently utilized in a saturated state.